Gel-Tank is a great game overall, but not without a few flaws. As I've spent too much time playing this game, I am going to list them all.
The first stages of Gel-Tank can be described as "dull Metal Slug". The core gameplay is solid, and it simulates the mechanics of Metal Slug well, but the game is noticeably easier. The action picks up over time, things become more fun and challenging, but the feeling that this was made by somebody who felt overwhelmed by Metal Slug's level design remains. No timer, mostly unrestricted movement through the level and a limited number of enemies make enemy encounters more manageable, but more boring as a result. A lot of enemies can be picked off ahead of time from the edge of the screen, minimizing the threat (and challenge) outside of the fixed encounters where the game throws waves of enemies at you. And, even there, enemies usually tend to come in moderately sized groups from the same side of the screen. The difficulty rises very slowly and, by the time it starts feeling close to early stages of Metal Slug, you are already knocking on the final boss's door. Most bosses only show token resistance at best, and the first boss is the dreadfully overused background giant that stands there and telegraphs its punches, which you probably know from at least half a dozen different games by now.
The level design is pretty good for a run and gun game, but the platformer elements feel like an early concept that got shelved later in the development. The X button feature to take off your tank gear and switch to gel mode barely sees any use. There is an occasional secret where you are required to climb a wall or do a water jump, but those are very rare, and there is next to no reason to do it during normal gameplay, except maybe to climb out of a pit. There is a grand total of two levels where you have to avoid enemy fire while climbing a wall, and the game forgets about water jumping entirely after the first few levels. Orange gem pickups that are worth 100 points disappear around the same time, only to come back for one last farewell a few worlds later.
The game features a customization system, with a good number of skills and limited skill slots available. Weapon rack skills let you take secondary weapons with you on a mission, saving you the headache of having to search for them during the mission or risking losing them. Weapon upgrades improve individual weapons, though not to the point that would make missile, flame shot and tomahawk worth using. "Tank/Bike/Warder Bring" skills let you spawn a vehicle at the beginning of the mission. A whole bunch of things that are now standard for the genre are also purchasable, like double (and triple) jump, faster movement, longer invincibility, attracting item pickups, etc. These skills serve well enough to make the game easier on its second highest difficulty setting, Classic, without removing the challenge entirely. The highest difficulty, Expert, appears to be inspired by the Megaman Zero series, as all it does is limit your health bar to 3 hits and disable all of your skills. The Time Attack skill also takes up most of the skill slots, leaving you with only one, but it also sets the difficulty to Standard, so the timer will be your only challenge in that mode. The nonexistent platforming that was mentioned before makes triple jump useless as well, as trying to use it to get past those cliffs that stop you from climbing a wall usually brings you to a very apparent edge of the map that they were blocking.
The audio and visual direction of the game also attracts comparison to Metal Slug, and Gel-Tank isn't as impressive here, either. There is not nearly as much attention to detail in spritework and sound design. The enemies are not expressive at all, which wouldn't be an issue if the game wasn't making nods to familiar scenes from Metal Slug, like the first train level that is supposed to resemble that one mission from Metal Slug 2. Nonetheless, Gel-Tank looks and sounds good in its own right. Nameko-san's art is as cute as ever. The music is nice. Mission debriefing scenes are comfy. The intercepted communications that play mid-mission also serve to improve the mood in the absence of enemy reactions that Metal Slug has.
The game doesn't seem to have any egregious in-game bugs, but it crashed on me a few times, probably because it ran out of RAM. I want to assume that this is just Unity being Unity with a game that looks like it should run with minimal frame drops on PS1, but the state of the achievements page (with all but three achievements being called NEW_ACHIEVEMENT_NAME with NEW_ACHIEVEMENT_DESC, and Nekodolphin achievement having wrong description) suggests other possibilities, too.
Finally, Rita never uses her handgun, which is a massive disappointment.
Perhaps the biggest problem with Gel-Tank isn't even that the game itself is flawed. It makes sense to release a game that is less than perfect, since a developer's resources are limited, and minor issues can be improved upon in Gel-Tank 2. However, with Koki-san's next game being a turn-based RPG, rather than another game in the vein of Metal Slug, all that we are left with is an already good game that could be better, but never will.
This review may be critical in its tone, but, overall, Gel-Tank is a good game. It plays well enough, it looks and sounds decent. As far as indie platformers go, it is above average in just about every respect, and probably deserves more than the ~300 players that it has. 9/10, it's no Metal Slug.
